Field of the Invention
The invention relates to a method for operating a wind power plant having at least one rotor blade, the blade angle of which can be adjusted, wherein the wind power plant is operated with a predefinable reduced energy output set point.
Description of Related Art
With the operation of wind power plants it can occur that the wind power plants must be reduced in the power thereof due to external demands, for example from the network supplier, or due to disturbances. With a reduction of power of the wind power plant that is not caused by the operator of the wind power plant but rather by the network supplier for example, it is necessary to quantify the lost energy output because as a rule someone has to provide compensation payments for this output that was not realized.
If there is a wind measurement mast in the proximity of the wind power plant or the wind farm, the potential output of the wind power plant, when the wind power plant is operated with a reduced energy output set point, can be calculated using an existing power curve of the wind power plant in the performance-optimized normal mode of the wind power plant, by measuring an actual wind speed and transferring this into the power curve, or respectively the energy output curve of the wind power plant. For this purpose then, the actual energy output which is attained by the desired, or respectively predetermined reduction, must be measured. With the knowledge of the actual wind strength, the potential output is then determined using the power curve, or respectively energy output curve, of the wind power plant in the performance-optimized normal mode, and correspondingly the difference of these two energy outputs is formed, namely of the potential output of the wind power plant, which corresponds to the energy output that would be attained by the wind power plant in the performance-optimized normal mode with the present wind speed, and the actual measured reduced energy output due to the predetermined reduced energy output set point. This difference corresponds to the loss in the output and must be remunerated then by the network operator, for example, to the operator of the wind power plant.
Typically, however, there is no wind measurement mast in the proximity of a wind power plant, or respectively a wind farm, or respectively a wind measurement mast would indicate only approximate information about the actual wind speed at a wind power plant when for example, the wind power plant does not have freely inflowing wind or the wind measurement mast would not have appropriate freely inflowing wind, or respectively turbulent wind is present.
In addition, the idea to use a nacelle anemometer of the reduced power plant, or respectively the wind power plant, which is operated with a predefinable reduced energy output set point, is not suitable because the anemometer measurement is heavily distorted due to the rotor. For the performance-optimized normal mode of the wind power plant, static anemometer corrections are used for this purpose which, however, are not applicable to the anemometer measurement values when the wind power plant is operated at a predefined reduced energy output set point, thus outside of the performance-optimized normal mode.